Peroxides have, as a general property, a tendency to be flammable and explosive with some peroxides exhibiting such properties to a greater extent than others. For example, benzoyl peroxide may decompose when dry due to shock, friction, or static electricity. This property carries with it the obvious hazards to the users of these materials as well as to the manufacturers and intermediate handlers thereof. One particularly burdensome aspect of this property occurs during shipment of the peroxides. Accordingly, it has long been an object to provide flame resistant organic peroxide compositions. For example, U.S. Pat. No. 3,507,800 is directed to providing a flame resistant peroxide composition consisting essentially of three components—water, peroxide and solvent wherein the water is at least about 18 percent of the composition.
The safety and end-use advantage provided by water-soluble or water-emulsifiable peroxides is recognized. U.S. Pat. No. 3,825,509 describes a process for the suspension polymerization of vinyl chloride wherein the initiator is an aqueous emulsion of an organic peroxide in which the peroxide is present in an amount up to 19 weight percent. The surfactant used to prepare the aqueous peroxide emulsion is a combination of polyvinyl alcohol and polyoxyethylene sorbitan monolaurate. However, emulsions containing greater than about 19 percent by weight of organic peroxide are described as being too viscous and therefore difficult to handle.
There have been attempts in the past to make peroxide dispersions. U.S. Pat. Nos. 4,039,475 and 4,092,470 disclose stable, pumpable aqueous suspensions of organic peroxides using a mixture of a) nonionic emulsifiers having a maximum HLB value of 12.5 and b) nonionic emulsifiers having a minimum HLB value of 12.5 or anionic emulsifiers. U.S. Pat. No. 4,734,135 discloses aqueous suspensions of solid organic peroxides using a protective colloid, a surface active agent and water. U.S. Pat. No. 4,440,885 teaches emulsions of a solid organic peroxide using an emulsifier having an HLB value from about 9 to about 20, a hydrocarbon solvent and water.
Organic peroxides are used as initiators in polymerization operations such as for acrylic and polyester polymerizations. The organic peroxides such as benzoyl peroxide are commercially available as solutions/dispersions in phthalates such as dimethyl phthalate and dibutyl phthalate. Due to a perception of toxicity issues with phthalates, there is a current effort to discontinue their use in the production of polymers for certain uses.